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NGC 4214: Star Forming Galax
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| Title |
NGC 4214: Star Forming Galaxy |
| Explanation |
Dazzling displays of star formation abound across the face of galaxy NGC 4214, a mere 13 million light-years away in the northern constellation Canes Venatici [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Canes_Venatici.html ]. While this 1997 Hubble Space Telescope image [ http://oposite.stsci.edu/pubinfo/pr/2000/01/pr-photos.html ] shows the numerous faint, older stars of NGC 4214 [ http://heritage.stsci.edu/public/2000jan6/ngc4214table.html ], the most eye-catching features are the galaxy's bright young star clusters surrounded by fluorescent gas clouds. Sculpted [ http://antwrp.gsfc.nasa.gov/apod/ap990930.html ] into bubbles and filamentary shapes by energetic explosions [ http://antwrp.gsfc.nasa.gov/apod/ap990515.html ] and stellar winds [ http://antwrp.gsfc.nasa.gov/apod/ap991130.html ] from massive cluster stars, the clouds fluoresce in the intense stellar ultraviolet radiation. The colorful [ http://www.c3.lanl.gov/mega-math/workbk/map/map.html ] spectacle of massive young star forming clusters and distinguished presence of a fainter, older stellar population indicate that NGC 4214 has experienced star formation [ http://observe.ivv.nasa.gov/nasa/exhibits/stellarbirth/ Star_index.html ] episodes spanning billions of years. |
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Celebrating Hubble With NGC
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| Title |
Celebrating Hubble With NGC 6751 |
| Explanation |
Planetary nebulae do [ http://antwrp.gsfc.nasa.gov/apod/ap991023.html ] look simple, round, and planet-like in small telescopes. But images from the orbiting Hubble Space Telescope [ http://hubble.stsci.edu/ ] have become well known for showing these fluorescent gas shrouds [ http://antwrp.gsfc.nasa.gov/apod/ap991031.html ] of dying Sun-like stars to possess a staggering variety [ http://oposite.stsci.edu/pubinfo/pr/97/pn/index.html ] of detailed symmetries and shapes. This composite color Hubble image of NGC 6751 [ http://oposite.stsci.edu/pubinfo/pr/2000/12/index.html ] is a beautiful example of a classic planetary nebula with complex features and was selected to commemorate the tenth anniversary [ http://pao.gsfc.nasa.gov/gsfc/spacesci/hst10/hst_main.htm ] of Hubble in orbit. The colors were chosen to represent the relative temperature of the gas - blue, orange, and red indicating the hottest to coolest gas. Winds and radiation from the intensely hot central star [ http://antwrp.gsfc.nasa.gov/apod/ap990703.html ] (140,000 degrees [ http://www.unidata.ucar.edu/staff/ blynds/tmp.html ] Celsius [ http://www.cchem.berkeley.edu/ChemResources/ temperature.html ]) have apparently created the nebula's streamer-like features. The nebula's [ http://heritage.stsci.edu/public/2000apr6/ ngc6751table.html ] actual diameter is approximately 0.8 light-years or about 600 times the size [ http://antwrp.gsfc.nasa.gov/apod/ap990916.html ] of our solar system. NGC 6751 is 6,500 light-years distant in the constellation Aquila [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Aquila.html ]. |
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A Dust Cloud in NGC 281
| Title |
A Dust Cloud in NGC 281 |
| Explanation |
Stars themselves can create huge and intricate dust sculptures [ http://antwrp.gsfc.nasa.gov/apod/ap050425.html ] from the dense and dark molecular cloud [ http://antwrp.gsfc.nasa.gov/apod/ap060409.html ]s from which they are born. The tools the stars use to carve their detailed works are high energy light [ http://imagers.gsfc.nasa.gov/ems/uv.html ] and fast stellar winds [ http://antwrp.gsfc.nasa.gov/apod/ap000318.html ]. The heat they generate evaporates the dark molecular dust [ http://en.wikipedia.org/wiki/Interstellar_dust ] as well as causing ambient hydrogen [ http://periodic.lanl.gov/elements/1.html ] gas to disperse and glow [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] red. Pictured above [ http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/13/image/a ], a new open cluster of stars designated IC 1590 is nearing completion around the intricate interstellar mountain [ http://antwrp.gsfc.nasa.gov/apod/ap050424.html ] named NGC 281 [ http://heritage.stsci.edu/2006/13/caption.html ]. The dust cloud NGC 281, dubbed the Pacman [ http://en.wikipedia.org/wiki/Pacman ] nebula because of its overall shape [ http://antwrp.gsfc.nasa.gov/apod/ap050823.html ], is classified as a dense Bok Globule [ http://antwrp.gsfc.nasa.gov/apod/ap030127.html ] that lies about 10,000 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] distant. |
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NGC 6164: A Bipolar Emission
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| Title |
NGC 6164: A Bipolar Emission Nebula |
| Explanation |
How did a star form this beautiful nebula? In the middle of emission nebula [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] NGC 6164-5 is an unusually massive star nearing the end of its life. The star, visible in the center of the above image [ http://www.gemini.edu/dualneb ] and catalogued as HD 148937, is so hot that the ultraviolet light [ http://imagers.gsfc.nasa.gov/ems/uv.html ] it emits heats up gas that surrounds it. That gas was likely thrown off from the star, possibly by its fast rotation, like a rotating lawn sprinkler. Expelled material might have been further channeled by the magnetic field [ http://antwrp.gsfc.nasa.gov/apod/ap980629.html ] of the star, creating the symmetric shape [ http://antwrp.gsfc.nasa.gov/apod/ap060326.html ] of the bipolar nebula [ http://antwrp.gsfc.nasa.gov/apod/ap030113.html ]. Several cometary knots [ http://antwrp.gsfc.nasa.gov/apod/ap960416.html ] of gas are also visible on the lower left. NGC 6164-5 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1985PASP...97..780F&] spans about four light years [ http://en.wikipedia.org/wiki/Light_years ] and is located about 4,000 light years away toward the southern constellation Norma [ http://www.seds.org/Maps/Stars_en/Fig/norma.html ]. |
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NGC 3314: When Galaxies Over
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| Title |
NGC 3314: When Galaxies Overlap |
| Explanation |
Can this be a spiral galaxy? In fact, NGC 3314 [ http://oposite.stsci.edu/pubinfo/pr/2000/14/index.html ] consists of two large spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap980314.html ] which just happen to almost exactly line-up. The foreground spiral is viewed nearly face-on, its pinwheel shape defined by young bright star clusters. But against the glow of the background galaxy, dark swirling lanes of interstellar dust [ http://antwrp.gsfc.nasa.gov/apod/ap980116.html ] are also seen [ http://antwrp.gsfc.nasa.gov/apod/ap971205.html ] to echo the face-on spiral's structure. The dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap990821.html ] are surprisingly pervasive, and this remarkable pair of [ http://www.astr.ua.edu/white/pairs/individual.html ] overlapping galaxies is one of a small number of systems in which absorption of visible light can be used to directly explore the distribution [ http://www.astr.ua.edu/white/pairs/thickthin.html ] of dust in distant spirals. NGC 3314 is [ http://heritage.stsci.edu/public/2000may11/about3314.html ] about 140 million light-years away in the southern constellation of Hydra [ http://www.astronomical.org/constellations/ hya.html ]. Just released [ http://heritage.stsci.edu/ ], this color composite was constructed from Hubble Space Telescope images made in 1999 and 2000. |
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A Galaxy Collision in NGC 67
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| Title |
A Galaxy Collision in NGC 6745 |
| Explanation |
Galaxies don't normally look like this. NGC 6745 [ http://heritage.stsci.edu/public/2000nov2/ngc6745story.html ] actually shows the results of two galaxies that have been colliding [ http://antwrp.gsfc.nasa.gov/apod/ap990722.html ] for only hundreds of millions of years. Just off the above photograph [ http://hubblesite.org/newscenter/archive/releases/2000/2000/34/image/a/ ] to the lower right is the smaller galaxy, moving away. The larger galaxy, pictured above [ http://heritage.stsci.edu/public/2000nov2/ngc6745table.html ], used to be a spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] but now is damaged and appears peculiar [ http://antwrp.gsfc.nasa.gov/apod/ap980315.html ]. Gravity has distorted the shapes of the galaxies. Although it is likely that no stars in the two galaxies directly collided [ http://antwrp.gsfc.nasa.gov/apod/ap061024.html ], the gas, dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ], and ambient magnetic fields [ http://www-spof.gsfc.nasa.gov/Education/Imagnet.html ] do interact directly. In fact, a knot [ http://www.mckinnonsc.vic.edu.au/school/ties/ties.htm ] of gas pulled off the larger galaxy on the lower right has now begun to form stars. NGC 6745 [ http://en.wikipedia.org/wiki/NGC_6745 ] spans about 80 thousand light-years across and is located about 200 million light-years [ http://www.howstuffworks.com/question94.htm ] away. |
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NGC 602 and Beyond
| Title |
NGC 602 and Beyond |
| Explanation |
Near the outskirts of the Small Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap050617.html ], a satellite galaxy some 200 thousand light-years distant, lies 5 million year young [ http://en.wikipedia.org/wiki/Stellar_evolution ] star cluster NGC 602. Surrounded by natal gas and dust, NGC 602 is featured in this stunning Hubble image [ http://hubblesite.org/newscenter/archive/releases/ 2007/04/ ] of the region. Fantastic [ http://antwrp.gsfc.nasa.gov/apod/ap061227.html ] ridges and swept back shapes strongly suggest that energetic radiation and shock waves from NGC 602's massive young stars have eroded the dusty material and triggered a progression of star formation [ http://heritage.stsci.edu/2007/04/supplemental.html ] moving away from the cluster's center. At the estimated distance of the Small Magellanic Cloud, the picture spans about 200 light-years, but a tantalizing [ http://hubblesite.org/newscenter/archive/releases/2007/04/ image/a/format/zoom ] assortment of background galaxies are also visible in the sharp Hubble view. The background galaxies [ http://www.noao.edu/outreach/aop/observers/ bggalaxies.html ] are hundreds of millions of light-years or more beyond NGC 602. |
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NGC 6960: The Witch's Broom
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| Title |
NGC 6960: The Witch's Broom Nebula |
| Explanation |
Ten thousand years ago, before the dawn of recorded human history [ http://news.bbc.co.uk/hi/english/sci/tech/newsid_334000/334517.stm ], a new light must suddenly have appeared in the night sky and faded after a few weeks. Today we know this light was an exploding star [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html ] and record the colorful expanding cloud as the Veil Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap010928.html ]. Pictured above [ http://www.noao.edu/image_gallery/html/im0852.html ] is the west end of the Veil Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap030204.html ] known technically as NGC [ http://en.wikipedia.org/wiki/New_General_Catalog ] 6960 but less formally as the Witch [ http://antwrp.gsfc.nasa.gov/apod/ap061211.html ]'s Broom [ http://www.broomshop.com/history/ ] Nebula. The rampaging gas gains its colors by impacting and exciting existing [ http://www.seds.org/billa/twn/cygnusx.html ] nearby gas. The supernova remnant [ http://antwrp.gsfc.nasa.gov/apod/supernova_remnants.html ] lies about 1400 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away towards the constellation of Cygnus [ http://www.multimania.com/cdadfs/constellation/cygne/cygnus.htm ]. This Witch's Broom actually spans over three times the angular size [ http://imagine.gsfc.nasa.gov/YBA/HTCas-size/more-ang_size.html ] of the full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap030810.html ]. The bright star 52 Cygnus [ http://www.seds.org/Maps/Stars_en/Fig/cygnus.html ] is visible with the unaided eye from a dark location but unrelated to the ancient supernova [ http://en.wikipedia.org/wiki/Supernova ]. |
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Planetary Nebula NGC 2440
| Title |
Planetary Nebula NGC 2440 |
| Explanation |
Planetary nebula [ http://en.wikipedia.org/wiki/Planetary_nebula ] NGC 2440 has an intriguing bow-tie [ http://www.folds.net/bowtie/ ] shape in this stunning view [ http://hubblesite.org/newscenter/archive/releases/2007/09/ ] from space. The nebula is composed of material cast off by a dying sun-like star as it enters its white dwarf phase [ http://antwrp.gsfc.nasa.gov/apod/ap060507.html ] of evolution. Details of remarkably complex structures are revealed within [ http://adsabs.harvard.edu/abs/1998ApJ...493..803L ] NGC 2440, including dense ridges of material swept back from the nebula's central star. Near the center of the view, the star itself is one of the hottest known [ http://antwrp.gsfc.nasa.gov/apod/ap951130.html ], with a surface temperature of about 200,000 kelvins [ http://lamar.colostate.edu/~hillger/temps.htm ]. About 4,000 light-years from planet Earth toward the nautical constellation Puppis [ http://hawastsoc.org/deepsky/pup/index.html ], the nebula spans over a light-year and is energized by ultraviolet light from the central star. The false-color image [ http://archive.stsci.edu/prepds/heritage/ngc2440/index.html ] was recorded earlier this month using the Hubble's Wide-Field Planetary Camera 2(WFPC2), demonstrating still impressive imaging capabilities following the failure of the Advanced Camera for Surveys. |
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Barred Spiral Galaxy NGC 167
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| Title |
Barred Spiral Galaxy NGC 1672 |
| Explanation |
Many spiral galaxies have bars across their centers. Even our own Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap000130.html ] is thought to have a modest central bar [ http://antwrp.gsfc.nasa.gov/apod/ap050825.html ]. Prominently barred spiral galaxy NGC 1672, pictured above [ http://hubblesite.org/newscenter/archive/releases/2007/15/image/a/ ], was captured in spectacular detail in this recently released image taken by the orbiting Hubble Space Telescope [ http://en.wikipedia.org/wiki/Hubble_Space_Telescope ]. Visible are dark filamentary dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap060219.html ], young clusters [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] of bright blue stars, red emission nebulas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] of glowing hydrogen gas, a long bright bar of stars across the center, and a bright active nucleus [ http://en.wikipedia.org/wiki/Active_galactic_nucleus ] that likely houses a supermassive black hole [ http://antwrp.gsfc.nasa.gov/htmltest/rjn_bht.html ]. Light takes about 60 million years to reach us from NGC 1672 [ http://heritage.stsci.edu/2007/15/caption.html ], which spans about 75,000 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] across. NGC 1672, which appears toward the constellation of the Swordfish (Dorado [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=33 ]), is being studied [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004hst..prop.6669J ] to find out how a spiral bar contributes to star formation in a galaxy's central regions. |
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In the Center of Reflection
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| Title |
In the Center of Reflection Nebula NGC 1333 |
| Explanation |
The dust is so thick in the center of NGC 1333 that you can hardly see the stars forming. Conversely, the very dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] clouds that hide the stars also reflects their optical light [ http://fuse.pha.jhu.edu/~wpb/spectroscopy/em_spec.html ], giving NGC 1333 [ http://www.robgendlerastropics.com/NGC1333text.html ]'s predominantly blue glow the general designation of a reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ]. A highly detailed image of the nebula, shown above [ http://www.noao.edu/image_gallery/html/im1037.html ], was taken recently by the Mayall 4-meter telescope [ http://www.noao.edu/outreach/kptour/mayall.html ] on Kitt Peak [ http://www.noao.edu/kpno/ ] in Arizona [ http://en.wikipedia.org/wiki/Arizona ], USA [ http://en.wikipedia.org/wiki/United_States ] and released to honor astronomer Stephen Strom [ http://www.noao.edu/outreach/press/pr07/pr0706.html ] on his retirement. Visible near the image top are vast blue regions of dust [ http://antwrp.gsfc.nasa.gov/apod/ap061211.html ] predominantly reflecting the light from bright massive stars [ http://antwrp.gsfc.nasa.gov/apod/ap060109.html ]. Visible in the thick central dust are not only newly formed stars but red jets [ http://antwrp.gsfc.nasa.gov/apod/ap070430.html ] and red-glowing gas energized by the light and winds [ http://www-spof.gsfc.nasa.gov/Education/wsolwind.html ] from recently formed young stars. The NGC 1333 [ http://adsabs.harvard.edu/abs/2002ApJ...580..959N ] nebula contains [ http://antwrp.gsfc.nasa.gov/apod/ap061006.html ] hundreds of newly formed stars that are less than one million years old. Reflection nebula [ http://en.wikipedia.org/wiki/Reflection_nebula ] NGC 1333 lies about 1,000 light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away toward the constellation of Perseus [ http://chandra.harvard.edu/photo/constellations/perseus.html ]. |
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NGC 4449: Close-Up of a Smal
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| Title |
NGC 4449: Close-Up of a Small Galaxy |
| Explanation |
Grand spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap030524.html ] often seem to get all the glory. Their newly formed, bright, blue star clusters along beautiful, symmetric spiral arms [ http://antwrp.gsfc.nasa.gov/apod/ap070706.html ] are guaranteed to attract attention. But small irregular galaxies form stars too, like NGC 4449 [ http://www.seds.org/~spider/spider/Misc/n4449.html ], located about 12 million light-years away. In fact, this sharp Hubble [ http://heritage.stsci.edu/2007/26/ ] Space Telescope close-up of the well-studied [ http://arxiv.org/abs/astro-ph/0010515 ] galaxy clearly demonstrates that reddish star forming regions and young blue star clusters are widespread [ http://hubblesite.org/newscenter/archive/releases/2007/26/ image/a/format/zoom/ ]. Less than 20,000 light-years across, the small island universe is similar in size, and often compared [ http://heritage.stsci.edu/2007/26/supplemental.html ] to our Milky Way's satellite galaxy, the Large Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap060510.html ]. NGC 4449 is a member of a group of galaxies [ http://www.atlasoftheuniverse.com/galgrps/cvni.html ] found in the constellation Canes Venatici. |
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NGC 3132: The Eight Burst Ne
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| Title |
NGC 3132: The Eight Burst Nebula |
| Explanation |
It's the dim star, not the bright one, near the center of NGC 3132 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997AAS...191.1508S&db_key=AST&high=34f6e1de7f27502 ] that created this odd but beautiful planetary nebula [ http://www.seds.org/messier/planetar.html ]. Nicknamed the Eight-Burst Nebula and the Southern Ring Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap000716.html ], the glowing gas originated in the outer layers [ http://antwrp.gsfc.nasa.gov/apod/ap010301.html ] of a star like our Sun [ http://www.nineplanets.org/sol.html ]. In this representative color picture [ http://heritage.stsci.edu/public/Nov5/NGC3132table.html ], the hot blue pool of light seen surrounding this binary system [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ] is energized by the hot surface of the faint star. Although photographed to explore [ http://archive.stsci.edu/cgi-bin/prop_search?6221 ] unusual symmetries, it's the asymmetries that help make this planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ] so intriguing. Neither the unusual shape of the surrounding cooler shell nor the structure and placements of the cool filamentary dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap990919.html ] running across NGC 3132 [ http://heritage.stsci.edu/public/Nov5/n3132filters.html ] are well understood. |
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Spiral Galaxy NGC 7742
| Title |
Spiral Galaxy NGC 7742 |
| Explanation |
This might resemble [ http://oposite.stsci.edu/pubinfo/pr/1998/28/index.html ] a fried egg you've had for breakfast [ http://antwrp.gsfc.nasa.gov/apod/ap980320.html ], but it's actually much larger. In fact, ringed by blue-tinted star forming [ http://antwrp.gsfc.nasa.gov/apod/ap980701.html ] regions and faintly visible spiral arms [ http://antwrp.gsfc.nasa.gov/apod/ap000920.html ], the yolk-yellow center of this face-on spiral galaxy, NGC 7742, is about 3,000 light-years across. About 72 million light-years [ http://www.treasure-troves.com/astro/Light-Year.html ] away in the constellation Pegasus [ http://www.seds.org/Maps/Stars_en/Fig/pegasus.html ], NGC 7742 is known to be a Seyfert galaxy [ http://www.astro.soton.ac.uk/PH308/AGN/Seyferts.html ] - a type of active spiral galaxy [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/active_galaxies.html ] with a center or nucleus which is very bright at visible wavelengths [ http://amazing-space.stsci.edu/light/index.html ]. Across the spectrum, the tremendous brightness [ http://seds.lpl.arizona.edu/messier/more/m077_hst.html ] of Seyferts [ http://www.seds.org/~spider/spider/ScholarX/seyferts.html ] can change over periods of just days to months and galaxies like NGC 7742 are suspected of harboring massive black holes at their cores [ http://oposite.stsci.edu/pubinfo/pr/97/18.html ]. This beautiful color picture is courtesy of the Hubble Space Telescope Heritage Project [ http://heritage.stsci.edu/public/commonpages/subjectindex.html ]. |
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Starburst Cluster in NGC 360
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| Title |
Starburst Cluster in NGC 3603 |
| Explanation |
A mere 20,000 light-years from the Sun lies NGC 3603 [ http://www.univie.ac.at/webda/cgi-bin/ ocl_page.cgi?cluster=NGC+3603 ], a resident of the nearby Carina spiral arm of our Milky Way Galaxy [ http://www.atlasoftheuniverse.com/milkyway.html ]. NGC 3603 is [ http://antwrp.gsfc.nasa.gov/apod/ap020814.html ] well known to astronomers as one of the Milky Way's largest star-forming regions. The central open star cluster contains thousands of stars more massive than our Sun, stars that likely formed only one or two million years ago in a single burst of star formation. In fact, nearby NGC 3603 [ http://hubblesite.org/newscenter/archive/releases/2007/34/image/ a/format/zoom/ ] is thought to contain a convenient example of the massive star clusters that populate much more distant starburst galaxies [ http://casswww.ucsd.edu/public/tutorial/Starbursts.html ]. Surrounding the cluster [ http://heritage.stsci.edu/2007/34/supplemental.html ] are natal clouds of glowing interstellar gas and obscuring dust, sculpted by energetic stellar radiation and winds. Recorded by [ http://heritage.stsci.edu/2007/34/fast_facts.html ] the Hubble's Advanced Camera for Surveys, the image spans about 17 light-years. |
|
NGC 3132: The Eight Burst Ne
…
| Title |
NGC 3132: The Eight Burst Nebula |
| Explanation |
It's the dim star, not the bright one, near the center of NGC 3132 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query? bibcode=1997AAS...191.1508S ] that created this odd but beautiful planetary nebula [ http://www.seds.org/messier/planetar.html ]. Nicknamed the Eight-Burst Nebula [ http://en.wikipedia.org/wiki/NGC_3132 ] and the Southern Ring Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap060625.html ], the glowing gas originated in the outer layers [ http://antwrp.gsfc.nasa.gov/apod/ap010301.html ] of a star like our Sun [ http://www.nineplanets.org/sol.html ]. In this representative color picture [ http://heritage.stsci.edu/1998/39/supplemental.html ], the hot blue pool of light seen surrounding this binary system [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ] is energized by the hot surface of the faint star. Although photographed to explore [ http://hubblesite.org/newscenter/archive/releases/1998/39/image/a/ ] unusual symmetries, it's the asymmetries that help make this planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ] so intriguing. Neither the unusual shape of the surrounding cooler shell nor the structure and placements of the cool filamentary dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap020703.html ] running across NGC 3132 [ http://heritage.stsci.edu/1998/39/index.html ] are well understood. |
|
Spiral Galaxy NGC 3310 Acros
…
| Title |
Spiral Galaxy NGC 3310 Across the Visible |
| Explanation |
The party is still going on in spiral galaxy NGC 3310. Roughly 100 million years ago, NGC 3310 [ http://antwrp.gsfc.nasa.gov/apod/ap010117.html ] likely collided with a smaller galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap001102.html ] causing the large spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] to light up with a tremendous burst of star formation [ http://archive.ncsa.uiuc.edu/Cyberia/Bima/StarForm.html ]. The changing gravity during the collision created density waves [ http://fuse.pha.jhu.edu/~danforth/spiral/ ] that compressed existing clouds of gas and triggered the star-forming party [ http://antwrp.gsfc.nasa.gov/apod/ap010812.html ]. The above image [ http://heritage.stsci.edu/public/2001sep/table.html ] composite by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] was used to find the ages of many of the resulting clusters [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] of stars. To the surprise of many, some of the clusters [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ] are quite young, indicating that starburst galaxies [ http://chandra.harvard.edu/xray_sources/starburst.html ] may remain in star-burst mode for quite some time. NGC 3310 [ http://home.cc.umanitoba.ca/~umnorri1/ngc3310intro.html ] spans about 50,000 light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ], lies about 50 million light years away, and is visible with a small telescope [ http://es.rice.edu/ES/humsoc/Galileo/Things/telescope.html ] towards the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Ursa Major [ http://www.astronomical.org/constellations/uma.html ]. |
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NGC 2346: A Butterfly-Shaped
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| Title |
NGC 2346: A Butterfly-Shaped Planetary Nebula |
| Explanation |
It may look like a butterfly, but it's bigger than our Solar System [ http://www.seds.org/nineplanets/nineplanets/overview.html ]. NGC 2346 [ http://heritage.stsci.edu/public/99oct7/ngc2346/ngc2346table.html ] is a planetary nebula [ http://www.noao.edu/jacoby/pn_gallery.html ] made of gas and dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] that has evolved into a familiar shape [ http://www.aao.gov.au/images/captions/aat079.html ]. At the heart of the bipolar planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap001217.html ] is a pair of close stars orbiting each other once every sixteen days. The tale [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1985ApJ...297..245S ] of how the butterfly blossomed probably began millions of years ago, when the stars were farther apart. The more massive star expanded to encompass its binary [ http://antwrp.gsfc.nasa.gov/apod/ap991219.html ] companion, causing the two to spiral closer and expel rings [ http://antwrp.gsfc.nasa.gov/apod/ap010729.html ] of gas. Later, bubbles of hot gas emerged as the core of the massive red giant star [ http://plabpc.csustan.edu/astro/stars/giant.htm ] became uncovered. In billions of years, our Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ] will become a red giant [ http://antwrp.gsfc.nasa.gov/apod/ap010630.html ] and emit a planetary nebula [ http://www.blackskies.com/index1.html ] - but probably not in the shape of a butterfly [ http://www.si.edu/resource/faq/nmnh/buginfo/butterfly.htm ], because the Sun [ http://www.windows.ucar.edu/cgi-bin/tour.cgi?link=/sun/sun.html ] has no binary star [ http://astrosun.tn.cornell.edu/courses/astro201/binstar.htm ] companion. |
|
Local Group Galaxy NGC 6822
| Title |
Local Group Galaxy NGC 6822 |
| Explanation |
Nearby galaxy NGC 6822 [ http://www.seds.org/messier/xtra/ngc/n6822.html ] is irregular in several ways. First, the galaxy's star distribution merits a formal classification of dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap001023.html ] irregular [ http://www.seds.org/messier/irre.html ], and from our vantage-point the small galaxy appears nearly rectangular. What strikes astronomers as more peculiar, however, is NGC 6822 [ http://www.ctio.noao.edu/REU/ctioreu_2001/shay/pagelgs.html ]'s unusually high abundance of HII regions [ http://antwrp.gsfc.nasa.gov/apod/ap011218.html ], locales of ionized [ http://csep10.phys.utk.edu/astr162/lect/light/ionization.html ] hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] that surround young stars. Large HII regions, also known as emission nebulas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], are visible [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1925ApJ....62..409H ] surrounding the small galaxy, particularly toward the upper right. Toward the lower left are bright stars that are loosely grouped into an arm. Pictured above [ http://www.noao.edu/image_gallery/html/im0698.html ], NGC 6822, also known as Barnard's Galaxy [ http://www.noao.edu/outreach/aop/observers/n6822.html ], is located only about 1.5 million light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away and so is a member of our Local Group of Galaxies [ http://www.seds.org/messier/more/local.html ]. The galaxy [ http://www.aao.gov.au/images/captions/aat026.html ], home to famous nebulas including Hubble V [ http://antwrp.gsfc.nasa.gov/apod/ap011225.html ], is visible with a small telescope toward the constellation [ http://www.adlerplanetarium.org/history/exhibits/constellations/ ] of Sagittarius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sagittarius.html ]. |
|
NGC 4631: The Whale Galaxy
| Title |
NGC 4631: The Whale Galaxy |
| Explanation |
NGC 4631 [ http://seds.lpl.arizona.edu/messier/xtra/ngc/n4631.html ] is a big beautiful spiral galaxy seen edge-on [ http://antwrp.gsfc.nasa.gov/apod/ap010510.html ] only 25 million light-years away towards the small northern constellation Canes Venatici [ http://seds.lpl.arizona.edu/messier/map/CVn.html ]. This galaxy's slightly distorted wedge shape suggests to some a cosmic herring and to others the popular moniker of The Whale Galaxy. Either way [ http://www.aemann.pwp.blueyonder.co.uk/paintings/ galaxy.html ], it is similar in size to our own Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap980523.html ]. In this gorgeous color image [ http://www.noao.edu/outreach/aop/observers/ n4631.html ], the Whale's dark interstellar dust clouds, young bright blue star clusters, and purplish star forming regions are easy to spot [ http://antwrp.gsfc.nasa.gov/apod/ap990507.html ]. A companion [ http://antwrp.gsfc.nasa.gov/apod/ap010804.html ] galaxy, the small elliptical NGC 4627 appears above the Whale Galaxy. Out of view off the lower left corner of the picture lies another distorted galaxy, the hockey stick-shaped NGC 4656 [ http://www.noao.edu/outreach/aop/observers/n4656.html ]. The distortions and mingling trails [ http://antwrp.gsfc.nasa.gov/apod/ap970224.html ] of gas and dust [ http://www.astro.uni-bonn.de/~nneini/coldust.html ] detected at other wavelengths suggest that all three galaxies have had close encounters with each other in their past. The Whale Galaxy is also known to have spouted a halo of hot gas glowing in x-rays [ http://chandra.harvard.edu/press/01_releases/press_071901.html ]. |
|
NGC 2359: Thor's Helmet
| Title |
NGC 2359: Thor's Helmet |
| Explanation |
NGC 2359 is a striking emission nebula [ http://www.noao.edu/outreach/aop/observers/ n2359.html ] with an impressive popular name - Thor's [ http://www.pantheon.org/ articles/t/thor.html ] Helmet. Sure, its suggestive winged appearance might lead some to refer to it as the "duck nebula", but if you were a nebula which name would you choose? By any name NGC 2359 [ http://www.kopernik.org/images/archive/ n2359.htm ] is a bubble-like nebula some 30 light-years across, blown by energetic winds from an extremely hot star [ http://www.star.ucl.ac.uk/~hsn/ ] seen near the center and classified as a Wolf-Rayet star. Wolf-Rayet stars [ http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/ 980603a.html ] are rare massive blue giants which develop stellar winds with speeds of millions of kilometers per hour. Interactions with [ http://antwrp.gsfc.nasa.gov/apod/ap970102.html ] a nearby large molecular cloud are thought to have contributed to this nebula's more complex shape and curved bow-shock [ http://antwrp.gsfc.nasa.gov/apod/ap010221.html ] structures. NGC 2359 is about 15,000 light-years distant toward the constellation [ http://www.hawastsoc.org/deepsky/cma/ ] Canis Major [ http://www.internal.org/view_poem.phtml?poemID=115 ]. |
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Open Star Clusters M35 and N
…
| Title |
Open Star Clusters M35 and NGC 2158 |
| Explanation |
Open clusters of stars can be near or far, young or old, and diffuse or compact. Open clusters [ http://www.seds.org/messier/open.html ] may contain from 100 to 10,000 stars, all of which formed at nearly the same time. Bright blue stars [ http://antwrp.gsfc.nasa.gov/apod/ap021201.html ] frequently distinguish younger open clusters. M35 [ http://www.seds.org/messier/m/m035.html ], pictured above [ http://www.noao.edu/image_gallery/html/im0794.html ] on the upper left, is a relatively nearby at 2800 light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] distant, relatively young at 150 million years old, and relatively diffuse, with about 2500 stars spread out over a volume 30 light years across. An older and more compact open cluster, NGC 2158 [ http://www.sciencenet.org.uk/astron/const/Gemini/ngc2158.html ], is visible above [ http://www.noao.edu/image_gallery/html/im0794.html ] on the lower right. NGC 2158 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002MNRAS.332..705C ] is four times more distant that M35 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001ApJ...546.1006B ], over 10 times older, and much more compact as it contains many more stars in roughly the same volume of space. NGC 2158's bright blue stars have self-destructed [ http://heasarc.gsfc.nasa.gov/docs/snr.html ], leaving cluster light to be dominated by older and yellower star [ http://antwrp.gsfc.nasa.gov/apod/ap000815.html ]s. Both clusters are visible toward the constellation [ http://www.adlerplanetarium.org/history/exhibits/constellations/timeline.html ] of Gemini [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Gemini.html ] -- M35 with binoculars and NGC 2158 with a small telescope. |
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NGC 253: The Sculptor Galaxy
| Title |
NGC 253: The Sculptor Galaxy |
| Explanation |
NGC 253 [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?ngc+253 ] is not only one of the brightest spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap980922.html ] visible, it is also one of the dustiest [ http://antwrp.gsfc.nasa.gov/apod/ap980116.html ]. Discovered in 1783 by Caroline Herschel [ http://history.math.csusb.edu/Mathematicians/Herschel_Caroline.html ] in the constellation of Sculptor [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sculptor.html ], NGC 253 [ http://astro.nmsu.edu/~choopes/research.html ] lies only about ten million light-years distant. NGC 253 [ http://seds.lpl.arizona.edu/messier/xtra/ngc/n0253.html ] is the largest member of the Sculptor Group of Galaxies [ http://seds.lpl.arizona.edu/messier/xtra/ngc/sclgr.html ], the nearest group to our own Local Group of Galaxies [ http://seds.lpl.arizona.edu/messier/more/local.html ]. The dense dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] accompanies a high star formation [ http://antwrp.gsfc.nasa.gov/apod/ap020717.html ] rate, giving NGC 253 [ http://antwrp.gsfc.nasa.gov/apod/ap990121.html ] the designation of starburst galaxy [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998ApJ...505..639E ]. Visible in the above photograph [ http://oposite.stsci.edu/pubinfo/pr/1998/42/a.html ] from the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] is the active central nucleus [ http://www.astr.ua.edu/keel/agn/text.html ], also known to be a bright source of X-rays [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#X-ray ] and gamma rays [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ]. |
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NGC 1275: A Galactic Collisi
…
| Title |
NGC 1275: A Galactic Collision |
| Explanation |
In NGC 1275, one galaxy is slicing through another. The disk of the dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ]y spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/spiral_galaxies.html ] near the image center is cutting through a large elliptical galaxy [ http://www.seds.org/messier/elli.html ], visible predominantly on the lower left. Galaxies [ http://www.damtp.cam.ac.uk/user/gr/public/gal_class.html ] can change significantly during a collision [ http://csep10.phys.utk.edu/astr162/lect/galaxies/colliding.html ] like this, with gravitational tides [ http://burro.astr.cwru.edu/Academics/Astr221/Gravity/tides.html ] distorting [ http://antwrp.gsfc.nasa.gov/apod/ap001102.html ] each galaxy and gas clouds being compressed [ http://www.aoc.nrao.edu/~smyers/courses/astro12/L14.html ] and lighting up with new star formation [ http://antwrp.gsfc.nasa.gov/apod/ap020611.html ]. Galaxy collisions [ http://antwrp.gsfc.nasa.gov/apod/ap020506.html ] occur in slow motion to the human eye [ http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/V/Vision.html ], with a single pass taking as much as 100 million years. NGC 1275 [ http://heritage.stsci.edu/2003/14/caption.html ] is a member of the Perseus cluster of galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap980815.html ] that lies about 230 million light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Perseus [ http://www.astronomical.org/constellations/per.html ]. Each galaxy spans about 50,000 light years across. The above picture [ http://heritage.stsci.edu/2003/14/index.html ] is a composite of images [ http://hubblesite.org/newscenter/archive/2003/14/ ] taken by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] in 1995 and 2001. |
|
The Stars of NGC 1705
| Title |
The Stars of NGC 1705 |
| Explanation |
Some 2,000 light-years across, NGC 1705 is small as galaxies go, similar to our Milky Way's own satellite galaxies, the Magellanic Clouds [ http://antwrp.gsfc.nasa.gov/apod/ap980203.html ]. At a much larger distance of 17 million light-years, the stars of NGC 1705 [ http://hubblesite.org/newscenter/archive/2003/07/image/a ] are still easily resolved in this beautiful image [ http://heritage.stsci.edu/2003/07/big.html ] constructed from data taken in 1999 and 2000 with the Hubble Space Telescope. Most of the younger, hot, blue [ http://antwrp.gsfc.nasa.gov/apod/ap961202.html ] stars in the galaxy are seen to be concentrated in a large central star cluster with the older, cooler [ http://antwrp.gsfc.nasa.gov/apod/ap010223.html ], red stars more evenly distributed. Possibly 13 billion years old, NGC 1705 [ http://hubblesite.org/newscenter/archive/2003/07/ fastfacts ] could well have been forming stars through out its lifetime while light from its most recent burst of star formation reached Earth only 30 million years ago. This gradually evolving dwarf irregular galaxy lacks organized [ http://hubblesite.org/newscenter/archive/1996/29/ astrofile#2 ] structures like spiral arms and is thought to be a nearby analog to the first galaxies [ http://www.ipac.caltech.edu/Outreach/Edu/early.html ] to form in the early Universe [ http://antwrp.gsfc.nasa.gov/apod/ap030212.html ]. |
|
Spiral Galaxy NGC 7742
| Title |
Spiral Galaxy NGC 7742 |
| Explanation |
This might resemble [ http://oposite.stsci.edu/pubinfo/pr/1998/28/index.html ] a fried egg you've had for breakfast [ http://antwrp.gsfc.nasa.gov/apod/ap980320.html ], but it's actually much larger. In fact, ringed by blue-tinted star forming [ http://antwrp.gsfc.nasa.gov/apod/ap980701.html ] regions and faintly visible spiral arms [ http://antwrp.gsfc.nasa.gov/apod/ap000920.html ], the yolk-yellow center of this face-on spiral galaxy, NGC 7742, is about 3,000 light-years across. About 72 million light-years [ http://www.treasure-troves.com/astro/ Light-Year.html ] away in the constellation Pegasus [ http://www.seds.org/Maps/Stars_en/Fig/ pegasus.html ], NGC 7742 is known to be a Seyfert galaxy [ http://www.seds.org/~spider/spider/ScholarX/ seyferts.html ] - a type of active spiral galaxy [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/ active_galaxies.html ] with a center or nucleus which is very bright at visible wavelengths [ http://amazing-space.stsci.edu/light/index.html ]. Across the spectrum, the tremendous brightness [ http://seds.lpl.arizona.edu/messier/more/ m077_hst.html ] of Seyferts can change over periods of just days to months and galaxies like NGC 7742 are suspected of harboring massive black holes at their cores [ http://oposite.stsci.edu/pubinfo/pr/97/18.html ]. This beautiful color picture is courtesy of the Hubble Space Telescope Heritage Project [ http://heritage.stsci.edu/public/commonpages/ subjectindex.html ]. |
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Blue Stragglers in NGC 6397
| Title |
Blue Stragglers in NGC 6397 |
| Explanation |
In our neck of the Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ] stars are too far apart [ http://antwrp.gsfc.nasa.gov/apod/ap991211.html ] to be in danger of colliding, but in the dense cores of globular star clusters [ http://antwrp.gsfc.nasa.gov/apod/ap010422.html ] star collisions may be relatively common. In fact, researchers have evidence [ http://www.aas.org/publications/baas/v32n2/aas196/ 265.htm ] that the closely spaced blue stars near the center of the above image [ http://heritage.stsci.edu/2003/21/caption.html ] taken by the orbiting Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] were formed when stars directly collided. Pictured is the central region of NGC 6397 [ http://www.seds.org/messier/xtra/ngc/n6397.html ], a globular cluster [ http://www.seds.org/messier/glob.html ] about 6,000 light-years distant, whose stars [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/ stars.html ] all formed at about the same time. NGC 6397's [ http://dibonsmith.com/ngc6397.htm ] massive stars have long since evolved off the main sequence [ http://observe.arc.nasa.gov/nasa/space/stellardeath/stellardeath_1ai.html ], exhausting their central supplies of nuclear fuel [ http://zebu.uoregon.edu/textbook/energygen.html ]. This should leave the cluster with only old low mass stars, faint red main sequence stars and brighter blue and red giants [ http://www.historyoftheuniverse.com/starold.html ]. However, spectroscopic data show that the indicated stars, descriptively dubbed blue stragglers [ http://antwrp.gsfc.nasa.gov/apod/ap971104.html ], are clearly main sequence stars which are too blue and too massive to still be there. Suggestively [ http://antwrp.gsfc.nasa.gov/apod/ap000622.html ] the stragglers appear to be two and occasionally three times as massive as the lower mass cluster stars otherwise present, supporting evidence [ http://heritage.stsci.edu/2003/21/supplemental.html ] for their formation from two and even three star collisions. |
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Copyright: AURA [ http://www
…
| Title |
Copyright: AURA [ http://www.aura-astronomy.org/ ] Explanation: Do star clusters form when galaxies collide? Quite possibly, according to Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap970306.html ] observations of the "Antennae [ http://wwwatnf.atnf.csiro.au/people/bkoribal/antennae.html ]", two galaxies thought to be in the early stages of a collision. As NGC 4038 and NGC 4039 [ http://crux.astr.ua.edu/gifimages/ngc4038.html ] slowly merge, the combined gravity of each pulls the other apart, huge gas clouds collide, and new bright stars and dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap961119.html ] are dispersed. Many blue knots of stars appear to be newly formed globular clusters [ http://antwrp.gsfc.nasa.gov/apod/ap970214.html ]. Red star knots [ http://isowww.estec.esa.nl/activities/info/iso_pr96/ngc4038.html ] are particularly interesting, as they might be globular clusters [ http://www.limber.org/globs.html ] that have not yet expelled early dust from their system. The above picture [ http://archive.stsci.edu/cgi-bin/hst_proposal_search?proposal_id=304&action=search&show=data+abs ] is centered around the smaller of the two interacting galaxies: NGC 4039. The color contrast [ http://oposite.stsci.edu/pubinfo/LookLike/ ] in the above three-color mosaic was chosen to highlight extended features. |
|
Copyright: AURA [ http://www
…
| Title |
Copyright: AURA [ http://www.aura-astronomy.org/ ] Explanation: This galaxy is having a bad millennium. In fact, the past 100 million years haven't been so good, and probably the next billion or so should be quite tumultuous. NGC 4039 [ http://adsbit.harvard.edu/cgi-bin/nph-article_query?bibcode=1995AJ%2E%2E%2E%2E109%2E%2E960W&page=1&plate_select=NO&type=GIF&nosetcookie=1 ] was a normal spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap970419.html ], minding its own business, when NGC 4038 [ http://antwrp.gsfc.nasa.gov/apod/ap970506.html ] crashed into it. The evolving wreckage, known as the "Antennae [ http://galileo.ifa.hawaii.edu/~hibbard/n4038/n4038.html ]", is pictured above. As gravity [ http://loner.ccsr.uiuc.edu/cyberprof/physics/101/Lecture/L13P3.html ] pulls each galaxy apart, clouds of gas slam into each other and bright blue knots are formed. These knots are large clusters of stars imbedded in vast regions of ionized hydrogen gas [ http://www.phys.unm.edu/~duric/l2h/l6/node1.html ]. The high abundance of relatively dim star clusters is quite unlike our Milky Way's globular cluster system [ http://www.limber.org/globs.html ], though. Perhaps some of these young star cluster [ http://antwrp.gsfc.nasa.gov/apod/ap970214.html ]s will go on to form globular clusters [ http://antwrp.gsfc.nasa.gov/apod/ap961004.html ], while others will disperse through close gravitational encounters. The above picture [ http://archive.stsci.edu/cgi-bin/hst_proposal_search?proposal_id=304&action=search&show=data+abs ] is centered around the larger of the two interacting galaxies: NGC 4038. The diagonal streak across the upper left is unrelated to the colliding galaxies. The color contrast [ http://oposite.stsci.edu/pubinfo/LookLike/ ] in the above three-color mosaic was chosen to highlight extended features. |
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NGC 604: Giant Stellar Nurse
…
| Title |
NGC 604: Giant Stellar Nursery |
| Explanation |
Stars are sometimes born in the midst of chaos. About 3 million years ago in the nearby galaxy M33 [ http://antwrp.gsfc.nasa.gov/apod/ap030924.html ], a large cloud of gas spawned dense internal knots which gravitationally collapsed to form stars. NGC 604 [ http://www.seds.org/messier/more/m033_n604.html ] was so large, however, it could form enough stars to make a globular cluster [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ]. Many young stars from this cloud are visible [ http://hubblesite.org/newscenter/newsdesk/archive/releases/2003/30/image/ ] in the above image [ http://heritage.stsci.edu/2003/30/caption.html ] from the Hubble Space Telescope [ http://www.stsci.edu/hst/HST_overview/ ], along with what is left of the initial gas cloud [ http://heritage.stsci.edu/2003/30/supplemental.html ]. Some stars were so massive they have already evolved and exploded in a supernova [ http://heasarc.gsfc.nasa.gov/docs/snr.html ]. The brightest stars [ http://antwrp.gsfc.nasa.gov/apod/ap021102.html ] that are left emit light so energetic that they create one of the largest cloud of ionized hydrogen [ http://antwrp.gsfc.nasa.gov/apod/ap030410.html ] gas known, comparable to the Tarantula Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap030823.html ] in our Milky Way [ http://www.damtp.cam.ac.uk/user/gr/public/gal_milky.html ]'s close neighbor, the Large Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap010804.html ]. |
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NGC 4631: The Whale Galaxy
| Title |
NGC 4631: The Whale Galaxy |
| Explanation |
NGC 4631 [ http://seds.lpl.arizona.edu/messier/xtra/ngc/n4631.html ] is a big beautiful spiral galaxy seen edge-on [ http://antwrp.gsfc.nasa.gov/apod/ap010510.html ] only 25 million light-years away towards the small northern constellation Canes Venatici [ http://seds.lpl.arizona.edu/messier/map/CVn.html ]. This galaxy's slightly distorted wedge shape suggests to some a cosmic herring and to others the popular moniker of The Whale Galaxy. Either way [ http://www.aemann.pwp.blueyonder.co.uk/paintings/ galaxy.html ], it is similar in size to our own Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap980523.html ]. In this gorgeous color image [ http://www.noao.edu/outreach/aop/observers/ n4631.html ], the Whale's dark interstellar dust clouds, young bright blue star clusters, and purplish star forming regions are easy to spot [ http://antwrp.gsfc.nasa.gov/apod/ap990507.html ]. A companion [ http://antwrp.gsfc.nasa.gov/apod/ap010804.html ] galaxy, the small elliptical NGC 4627 appears above the Whale Galaxy. Out of view off the lower left corner of the picture lies another distorted galaxy, the hockey stick-shaped NGC 4656 [ http://www.noao.edu/outreach/aop/observers/n4656.html ]. The distortions and mingling trails [ http://antwrp.gsfc.nasa.gov/apod/ap970224.html ] of gas and dust [ http://www.astro.uni-bonn.de/~nneini/coldust.html ] detected at other wavelengths suggest that all three galaxies have had close encounters with each other in their past. The Whale Galaxy is also known to have spouted a halo of hot gas glowing in x-rays [ http://chandra.harvard.edu/press/01_releases/press_071901.html ]. |
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NGC 6960: The Witch's Broom
…
| Title |
NGC 6960: The Witch's Broom Nebula |
| Explanation |
Ten thousand years ago, before the dawn of recorded human history [ http://news.bbc.co.uk/hi/english/sci/tech/newsid_334000/334517.stm ], a new light must suddenly have appeared in the night sky and faded after a few weeks. Today we know this light was an exploding star [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html ] and record the colorful expanding cloud as the Veil Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap010928.html ]. Pictured above [ http://www.noao.edu/image_gallery/html/im0852.html ] is the west end of the Veil Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap030204.html ] known technically as NGC [ http://www.ngcic.com/dss/dss_images.htm ] 6960 but less formally as the Witch [ http://antwrp.gsfc.nasa.gov/apod/ap031229.html ]'s Broom [ http://www.broomshop.com/history/ ] Nebula. The rampaging gas gains its colors by impacting and exciting existing [ http://www.seds.org/billa/twn/cygnusx.html ] nearby gas. The supernova remnant [ http://antwrp.gsfc.nasa.gov/apod/supernova_remnants.html ] lies about 1400 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away towards the constellation of Cygnus [ http://www.multimania.com/cdadfs/constellation/cygne/cygnus.htm ]. This Witch's Broom actually spans over three times the angular size [ http://imagine.gsfc.nasa.gov/YBA/HTCas-size/more-ang_size.html ] of the full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap030810.html ]. The bright star 52 Cygnus [ http://www.seds.org/Maps/Stars_en/Fig/cygnus.html ] is visible with the unaided eye from a dark location but unrelated to the ancient supernova [ http://www.chapman.edu/oca/benet/intro_sn.htm ]. |
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The Stars of NGC 300
| Title |
The Stars of NGC 300 |
| Explanation |
Like grains of sand [ http://astronomy.swin.edu.au/staff/gmackie/billions.html ] on a cosmic beach, individual stars of large spiral galaxy NGC 300 [ http://heritage.stsci.edu/2004/13/ ] are resolved in this sharp image from the Hubble Space Telescope's Advanced Camera for Surveys (ACS [ http://hubblesite.org/sci.d.tech/nuts_.and._bolts/ instruments/acs/ ]). The inner region of the galaxy is pictured [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2004/13/fastfacts/ ], spanning about 7,500 light-years. At its center is the bright, densely packed galactic core surrounded by a loose array of dark dust lanes mixed with the stars in the galactic plane. NGC 300 lies 6.5 million light-years away and is part of a group of galaxies [ http://www.seds.org/messier/xtra/ngc/sclgr.html ] named for the southern constellation Sculptor. Hubble's unique ability to distinguish so many stars [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2004/13/ ] in NGC 300 [ http://antwrp.gsfc.nasa.gov/apod/ap020821.html ] can be used to hone techniques [ http://www.ifa.hawaii.edu/%7Ebresolin/Araucaria/ ] for making distance measurements [ http://www.astro.ucla.edu/~wright/ distance.htm ] on extragalactic scales [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/ debate96.html ]. |
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NGC 4565: Galaxy on the Edge
| Title |
NGC 4565: Galaxy on the Edge |
| Explanation |
Magnificent spiral galaxy NGC 4565 [ http://www.seds.org/messier/xtra/ngc/n4565.html ] is viewed edge-on [ http://antwrp.gsfc.nasa.gov/apod/ap010510.html ] from planet Earth. Also known as the Needle Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap990617.html ] for its narrow profile, bright NGC 4565 is a stop on many springtime telescopic tours of the northern sky as it lies in the faint but well-groomed constellation Coma Berenices [ http://www.dibonsmith.com/com_con.htm ]. This sharp color image [ http://www.noao.edu/outreach/aop/observers/n4565.html ] reveals the galaxy's bulging central core dominated by light from a population of older, yellowish stars. The core is dramatically cut by obscuring dust lanes which lace NGC 4565's thin galactic plane. A large island universe [ http://nedwww.ipac.caltech.edu/level5/March02/ Gordon/Gordon2.html ] similar to our own Milky Way Galaxy [ http://cassfos02.ucsd.edu/public/tutorial/MW.html ], NGC 4565 is only about 30 million light-years distant, but over 100,000 light-years in diameter. In fact, some consider NGC 4565 to be a prominent celestial masterpiece Messier missed [ http://www.seds.org/pub/info/newsletters/ WASP/wasp_mmm.html#8 ]. |
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In the Center of NGC 6559
| Title |
In the Center of NGC 6559 |
| Explanation |
Bright gas and dark dust permeate the space between stars in the center of a nebula known as NGC 6559 [ http://www.noao.edu/outreach/aop/observers/n6559.html ]. The gas, primarily hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ], is responsible for the diffuse red glow of the emission nebula [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ]. As energetic light from neighboring stars ionizes interstellar hydrogen [ http://antwrp.gsfc.nasa.gov/apod/ap010113.html ], protons [ http://www.neutron.anl.gov/hyper-physics/proton.html ] and electrons [ http://www.aip.org/history/electron/ ] recombine to emit light [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ] of very specific colors [ http://csep10.phys.utk.edu/astr162/lect/light/absorption.html ], including the red [ http://antwrp.gsfc.nasa.gov/apod/ap010214.html ] hue observed. Small dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] particles reflect blue starlight efficiently and so creates the blue reflection nebulosity [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ] seen near two of the bright stars. Dust [ http://nedwww.ipac.caltech.edu/level5/Mathis/Mathis9.html ] also absorbs visible light, causing the dark clouds [ http://antwrp.gsfc.nasa.gov/apod/ap030202.html ] and filaments [ http://antwrp.gsfc.nasa.gov/apod/ap990919.html ] visible. NGC 6559 [ http://www.aao.gov.au/images/captions/uks003.html ] lies about 5000 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away toward the constellation of Sagittarius [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=72 ]. |
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NGC 2683: Spiral Edge-On
| Title |
NGC 2683: Spiral Edge-On |
| Explanation |
This gorgeous island universe [ http://nedwww.ipac.caltech.edu/level5/ March02/Gordon/Gordon2.html ], cataloged as NGC 2683 [ http://www.seds.org/~spider/spider/Misc/n2683.html ], lies a mere 16 million light-years distant in the northern constellation Lynx [ http://rao.150m.com/NGC2683.html ]. A spiral galaxy comparable to our own Milky Way, NGC 2683 is seen nearly edge-on [ http://antwrp.gsfc.nasa.gov/apod/ap010510.html ] in this cosmic vista [ http://www.noao.edu/outreach/aop/observers/n2683.html ], with more distant galaxies scattered in the background. Blended light from a large population of old yellowish stars forms the remarkably bright galactic core. Starlight silhouettes the dust lanes along winding spiral arms, dotted with the telltale pink glow [ http://antwrp.gsfc.nasa.gov/apod/ap041020.html ] of ionized hydrogen gas from this galaxy's star forming regions. |
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NGC 3132: The Eight Burst Ne
…
| Title |
NGC 3132: The Eight Burst Nebula |
| Explanation |
It's the dim star, not the bright one, near the center of NGC 3132 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query? bibcode=1997AAS...191.1508S&db_key=AST&high=34f6e1de7f27502 ] that created this odd but beautiful planetary nebula [ http://www.seds.org/messier/planetar.html ]. Nicknamed the Eight-Burst Nebula and the Southern Ring Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap040704.html ], the glowing gas originated in the outer layers [ http://antwrp.gsfc.nasa.gov/apod/ap010301.html ] of a star like our Sun [ http://www.nineplanets.org/sol.html ]. In this representative color picture [ http://heritage.stsci.edu/1998/39/supplemental.html ], the hot blue pool of light seen surrounding this binary system [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ] is energized by the hot surface of the faint star. Although photographed to explore [ http://archive.stsci.edu/cgi-bin/prop_search?6221 ] unusual symmetries, it's the asymmetries that help make this planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ] so intriguing. Neither the unusual shape of the surrounding cooler shell nor the structure and placements of the cool filamentary dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap020703.html ] running across NGC 3132 [ http://heritage.stsci.edu/1998/39/index.html ] are well understood. |
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Seyfert Galaxy NGC 7742
| Title |
Seyfert Galaxy NGC 7742 |
| Explanation |
This might resemble [ http://oposite.stsci.edu/pubinfo/pr/1998/28/index.html ] a fried egg you've had for breakfast [ http://antwrp.gsfc.nasa.gov/apod/ap980320.html ], but it's actually much larger. In fact, ringed by blue-tinted star forming [ http://antwrp.gsfc.nasa.gov/apod/ap980701.html ] regions and faintly visible spiral arms [ http://antwrp.gsfc.nasa.gov/apod/ap980326.html ], the yolk-yellow center of this face-on spiral galaxy, NGC 7742, is about 3,000 light-years across. About 72 million light-years away in the constellation Pegasus, NGC 7742 is known to be a Seyfert galaxy [ http://www.astro.soton.ac.uk/PH308/AGN/Seyferts.html ] - a type of active spiral galaxy [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/active_galaxies.html ] with a center or nucleus which is very bright at visible wavelengths [ http://oposite.stsci.edu/pubinfo/education/amazing-space/ light/ems-frames.html ]. Across the spectrum, the tremendous brightness [ http://seds.lpl.arizona.edu/messier/more/m077_hst.html ] of Seyferts can change over periods of just days to months and galaxies like NGC 7742 are suspected of harboring massive black holes at their cores [ http://oposite.stsci.edu/pubinfo/pr/97/18.html ]. This beautiful color picture is courtesy of the newly inaugurated Hubble Space Telescope Heritage Project [ http://heritage.stsci.edu/public/commonpages/subjectindex.html ]. |
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NGC 6946: The Fireworks Gala
…
| Title |
NGC 6946: The Fireworks Galaxy |
| Explanation |
Why is this galaxy so active? Nearby spiral galaxy NGC 6946 [ http://www.noao.edu/outreach/aop/observers/n6946.html ] is undergoing a tremendous burst of star formation with no obvious cause. In many cases spirals light up when interacting with another galaxy, but NGC 6946 [ http://antwrp.gsfc.nasa.gov/apod/ap040410.html ] appears relatively isolated in space. Located just 10 million light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away toward the constellation [ http://www.fillingthesky.com/id8.html ] of Cepheus [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=20 ], this beautiful face-on spiral [ http://antwrp.gsfc.nasa.gov/apod/ap041216.html ] spans about 20,000 light years and is seen through a field of foreground stars from our Milky Way Galaxy [ http://cassfos02.ucsd.edu/public/tutorial/MW.html ]. The center of NGC 6946 [ http://www.gemini.edu/index.php?option=content&task=view&id=116 ] is home to a nuclear starburst itself, and picturesque dark dust is seen lacing the disk along with bright blue stars [ http://antwrp.gsfc.nasa.gov/apod/ap031227.html ], red emission nebulas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], fast moving gas clouds, and unusually frequent supernovas [ http://heasarc.gsfc.nasa.gov/docs/snr.html ]. The 8-meter Gemini North Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap990629.html ] in Hawaii, USA [ http://www.cia.gov/cia/publications/factbook/geos/us.html ], took the above image [ http://www.gemini.edu/index.php?set_albumName=Previous-Featured-Images&id=ngc6946_Small&option=com_gallery&Itemid=39&include=view_photo.php ]. A suggested explanation [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000MNRAS.319..821P ] for the high star formation rate is the recent accretion of many primordial low-mass neutral hydrogen clouds [ http://www.universetoday.com/am/publish/clouds_hydrogen_swarm_andromeda.html?422004 ] from the surrounding region. |
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NGC 2467: From Gas to Stars
| Title |
NGC 2467: From Gas to Stars |
| Explanation |
One might guess that the group of stars on the left is responsible for shaping the gas cloud on the right -- but it probably is not. Observations of many of the stars in the NGC 2467 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1989A%26AS...77..321F ] show them to be more a superposition of loose groups of stars at different distances than a coherent open cluster [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] of stars energizing the nebula. Still, the above image [ http://www.gemini.edu/index.php?option=content&task=view&id=119&limitstart=1#ngc2467 ] captures various stages of star formation. The stars at the far left have already formed and their birth nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap041024.html ] have already dispersed. At the lower left lies a very young star that is breaking free of its surrounding birth cocoon [ http://antwrp.gsfc.nasa.gov/apod/ap030816.html ] of gas. On the right of the above image, a bright wall of bright gas glows as it evaporates [ http://antwrp.gsfc.nasa.gov/apod/ap031026.html ] from the energy of many newly formed bright stars. Toward the center, deep dark lanes [ http://antwrp.gsfc.nasa.gov/apod/ap040618.html ] of dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] hide parts of the nebula that surely are forming new stars. The 8-meter Gemini [ http://antwrp.gsfc.nasa.gov/apod/ap030909.html ] South Telescope [ http://www.gemini.edu/index.php?option=content&task=view&id=9&Itemid=2 ], perched on a mountaintop in Cerro Pachon [ http://nightskylive.net/cp/ ], Chile [ http://www.cia.gov/cia/publications/factbook/geos/ci.html ], took the above image [ http://www.gemini.edu/index.php?set_albumName=Previous-Featured-Images&id=ngc2467TNSMLRes&option=com_gallery&Itemid=39&include=view_photo.php ]. NGC 2467 lies toward the southern constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Puppis [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=68 ], with many of the stars being about 17,000 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] distant. |
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NGC 3132: The Eight Burst Ne
…
| Title |
NGC 3132: The Eight Burst Nebula |
| Explanation |
It's the dim star, not the bright one, near the center of NGC 3132 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997AAS...191.1508S&db_key=AST&high=34f6e1de7f27502 ] that created this odd but beautiful planetary nebula [ http://www.seds.org/messier/planetar.html ]. Nicknamed the Eight-Burst Nebula and the Southern Ring Nebula, the glowing gas originated in the outer layers of a star like our Sun [ http://www.hawastsoc.org/solar/eng/sun.htm ]. In this representative color picture [ http://oposite.stsci.edu/pubinfo/pr/1998/39/index.html ], the hot blue pool of light seen surrounding this binary system [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ] is energized by the hot surface of the faint star. Although photographed to explore [ http://archive.stsci.edu/cgi-bin/prop_search?6221 ] unusual symmetries, it's the asymmetries that help make NGC 3132 so intriguing. Neither the unusual shape of the surrounding cooler shell nor the structure and placements of the cool filamentary dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap980318.html ] running across NGC 3132 [ http://oposite.stsci.edu/pubinfo/pr/1998/39/content/prc9839.txt ] are well understood. |
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NGC 1531/2: Interacting Gala
…
| Title |
NGC 1531/2: Interacting Galaxies |
| Explanation |
This dramatic image of an interacting pair of galaxies [ http://www.astr.ua.edu/pairs2.html ] was made using 8-meter Gemini [ http://antwrp.gsfc.nasa.gov/apod/ap030909.html ] South telescope [ http://www.gemini.edu/index.php?option=content&task=view&id=9&Itemid=2 ] at Cerro Pachon [ http://nightskylive.net/cp/ ], Chile [ http://www.cia.gov/cia/publications/factbook/geos/ci.html ]. NGC 1531 is the background galaxy with a bright core just above center and NGC 1532 [ http://antwrp.gsfc.nasa.gov/apod/ap980710.html ] is the foreground spiral galaxy [ http://www.seds.org/messier/spir.html ] laced with dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] lanes. The pair [ http://www.noao.edu/image_gallery/html/im0983.html ] is about 55 million light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away in the southern constellation Eridanus [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Eridanus.html ]. These galaxies lie close enough together so that each feels the influence [ http://antwrp.gsfc.nasa.gov/apod/ap001102.html ] of the other's gravity [ http://www.curtin.edu.au/curtin/dept/phys-sci/gravity/history/history.htm ]. The gravitational tug-of-war [ http://www.army.mod.uk/sportandadventure/clubs/tug_of_war/history.htm ] has triggered star formation [ http://antwrp.gsfc.nasa.gov/apod/ap040414.html ] in the foreground spiral as evidenced by the young, bright blue star clusters [ http://antwrp.gsfc.nasa.gov/apod/ap050103.html ] along the upper edge of the front spiral arm [ http://www.astronomycafe.net/qadir/q2233.html ]. Though the spiral galaxy in this pair [ http://www.gemini.edu/index.php?option=content&task=view&id=119 ] is viewed nearly edge-on, astronomers believe the system is similar to the face-on spiral and companion known as M51, the Whirlpool Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap020710.html ]. |
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NGC 1427A: Galaxy in Motion
| Title |
NGC 1427A: Galaxy in Motion |
| Explanation |
In this tantalizing image [ http://heritage.stsci.edu/2005/09/ ], young blue star clusters [ http://antwrp.gsfc.nasa.gov/apod/ap990402.html ] and pink star-forming regions [ http://antwrp.gsfc.nasa.gov/apod/ap040909.html ] abound in NGC 1427A, a galaxy in motion. The small irregular [ http://antwrp.gsfc.nasa.gov/apod/ap991218.html ] galaxy's swept back outline points toward the top of this picture from the Hubble Space Telescope - and that is indeed the direction NGC 1427A is moving as it travels toward the center of the Fornax cluster [ http://heritage.stsci.edu/2005/09/supplemental.html ] of galaxies, some 62 million light-years away. Over 20,000 light-years long and similar to the nearby [ http://antwrp.gsfc.nasa.gov/apod/ap040902.html ] Large Magellanic Cloud, NGC 1427A is [ http://www.astro.uni-bonn.de/~mhilker/n1427a.html ] speeding through the Fornax cluster's intergalactic gas [ http://antwrp.gsfc.nasa.gov/apod/ap040924.html ] at around 600 kilometers per second. The resulting pressure is giving the galaxy its arrowhead outline and triggering the beautiful but violent episodes of star formation. Still, it is understood that interactions with cluster gas and the other cluster galaxies [ http://chandra.harvard.edu/xray_sources/ galaxy_clusters.html ] during its headlong flight will ultimately disrupt galaxy NGC 1427A [ http://heritage.stsci.edu/2005/09/caption.html ]. Many unrelated background galaxies are visible in the sharp Hubble image, including a striking face-on [ http://antwrp.gsfc.nasa.gov/apod/ap040410.html ] spiral galaxy at the upper left. |
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NGC 1316: After Galaxies Col
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| Title |
NGC 1316: After Galaxies Collide |
| Explanation |
How did this strange-looking galaxy form? Astronomers turn detectives when trying to figure out the cause of unusual jumbles of stars, gas, and dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] like NGC 1316 [ http://antwrp.gsfc.nasa.gov/apod/ap990222.html ]. A preliminary inspection indicates that NGC 1316 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004ASPC..322..469G ] is an enormous elliptical galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap991121.html ] that includes dark dust lanes usually found in a spiral. The above image [ http://heritage.stsci.edu/2005/11/index.html ] taken by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] shows details, however, that help in reconstructing the history of this gigantic jumble. Close inspection finds [ http://heritage.stsci.edu/2005/11/caption.html ] fewer low mass globular clusters [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ] of stars toward NGC 1316's center. Such an effect is expected in galaxies that have undergone collisions [ http://antwrp.gsfc.nasa.gov/apod/ap041121.html ] or merging with other galaxies in the past few billion years. After such collisions, many star clusters [ http://antwrp.gsfc.nasa.gov/apod/ap030915.html ] would be destroyed in the dense galactic center. The dark knots and lanes of dust [ http://antwrp.gsfc.nasa.gov/apod/ap020421.html ] indicate that one or more of the devoured galaxies were spiral [ http://antwrp.gsfc.nasa.gov/apod/ap001102.html ] galaxies. NGC 1316 [ http://antwrp.gsfc.nasa.gov/apod/ap000816.html ] spans about 60,000 light years and lies about 75 million light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of the Furnace [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=37 ]. |
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NGC 253: The Sculptor Galaxy
| Title |
NGC 253: The Sculptor Galaxy |
| Explanation |
NGC 253 is not only one of the brightest spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap980922.html ] visible, it is also one of the dustiest [ http://antwrp.gsfc.nasa.gov/apod/ap980116.html ]. Discovered in 1783 by Caroline [ http://history.math.csusb.edu/Mathematicians/Herschel_Caroline.html ] Herschel [ http://www.scottlan.edu/LRIDDLE/WOMEN/herschel.htm ] in the constellation of Sculptor [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sculptor.html ], NGC 253 [ http://astro.nmsu.edu/~choopes/research.html ] lies only about ten million light-years distant. NGC 253 [ http://seds.lpl.arizona.edu/messier/xtra/ngc/n0253.html ] is the largest member of the Sculptor Group of Galaxies [ http://seds.lpl.arizona.edu/messier/xtra/ngc/sclgr.html ], the nearest group to our own Local Group of Galaxies [ http://seds.lpl.arizona.edu/messier/more/local.html ]. The dense dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap980104.html ] accompanies a high star formation [ http://antwrp.gsfc.nasa.gov/apod/ap981207.html ] rate, giving NGC 253 [ http://antwrp.gsfc.nasa.gov/apod/ap961102.html ] the designation of starburst galaxy [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998ApJ...505..639E&db_key=AST&nosetcookie=1&high=33613e8e5801623 ]. Visible in the above photograph [ http://oposite.stsci.edu/pubinfo/pr/1998/42/a.html ] from the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ] is the active central nucleus, also known to be a bright source of X-rays [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#X-ray ] and gamma rays [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ]. |
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Celebrating Hubble With NGC
…
| Title |
Celebrating Hubble With NGC 6751 |
| Explanation |
Planetary nebulae can [ http://antwrp.gsfc.nasa.gov/apod/ap040424.html ] look simple, round, and planet-like in small telescopes. But images from the orbiting Hubble Space Telescope [ http://hubblesite.org/reference_desk/faq/ category.php.cat=hst ] have become well known for showing these fluorescent gas shrouds [ http://antwrp.gsfc.nasa.gov/apod/ap050311.html ] of dying Sun-like stars to possess a staggering variety [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ image_category/nebula/planetary/ ] of detailed symmetries and shapes [ http://antwrp.gsfc.nasa.gov/apod/ap040910.html ]. This composite color Hubble image of NGC 6751 [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2000/12/ ] is a beautiful example of a classic planetary nebula with complex features. It was selected in April of 2000, to commemorate the tenth anniversary [ http://hubblesite.org/newscenter/newsdesk/future/ ] of Hubble in orbit. The colors were chosen to represent the relative temperature of the gas - blue, orange, and red indicating the hottest to coolest gas. Winds and radiation from the intensely hot central star [ http://antwrp.gsfc.nasa.gov/apod/ap050123.html ] (140,000 degrees [ http://www.unidata.ucar.edu/staff/ blynds/tmp.html ] Celsius [ http://www.astro.uu.se/history/Celsius_eng.html ]) have apparently created the nebula's streamer-like features. The nebula's [ http://heritage.stsci.edu/2000/12/fast_facts.html ] actual diameter is approximately 0.8 light-years or about 600 times the size of our solar system. NGC 6751 is 6,500 light-years distant in the high-flying constellation Aquila [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Aquila.html ]. |
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NGC 3314: When Galaxies Over
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| Title |
NGC 3314: When Galaxies Overlap |
| Explanation |
NGC 3314 [ http://hubblesite.org/newscenter/newsdesk/archive/ releases/2000/14/ ] consists of two large spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap980314.html ] which just happen to almost exactly line-up. The foreground spiral is viewed nearly face-on [ http://antwrp.gsfc.nasa.gov/apod/ap040410.html ], its pinwheel shape defined by young bright star clusters. But against the glow of the background galaxy, dark swirling lanes of interstellar dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] are also seen to echo the face-on spiral's structure. The dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap990821.html ] are surprisingly pervasive, and this remarkable pair of [ http://www.astr.ua.edu/white/pairs/individual.html ] overlapping galaxies is one of a small number of systems in which absorption of visible light can be used to directly explore the distribution [ http://www.astr.ua.edu/white/pairs/thickthin.html ] of dust in distant spirals. NGC 3314 is [ http://hubblesite.org/newscenter/newsdesk/archive/ releases/2000/14/fastfacts/ ] about 140 million light-years away in the multi-headed constellation Hydra [ http://www.hawastsoc.org/deepsky/hya/index.html ]. This color composite was constructed from Hubble Space Telescope images made in 1999 and 2000. |
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Unusual Gas Filaments Surrou
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| Title |
Unusual Gas Filaments Surround Galaxy NGC 1275 |
| Explanation |
How were the unusual gas filaments surrounding galaxy NGC 1275 created? No one is sure. Galaxy NGC 1275 is the central dominant galaxy [ http://www.daviddarling.info/encyclopedia/D/D_galaxy.html ] of the Perseus Cluster of Galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap041025.html ], a cluster with many member galaxies visible in the above image. In visible light, NGC 1275 [ http://antwrp.gsfc.nasa.gov/apod/ap030505.html ] appears to show a spectacular collision [ http://antwrp.gsfc.nasa.gov/apod/ap040612.html ] between two distinct galaxies. The galaxy and cluster are also bright emitters of X-rays [ http://imagers.gsfc.nasa.gov/ems/xrays.html ]. The unusual gas filaments are shown above in a very specific color [ http://www.spaceweather.com/glossary/halpha.html ] of light emitted by hydrogen [ http://www.webelements.com/webelements/elements/text/H/key.html ], here artificially colored pink. Possible origins for the filaments [ http://arxiv.org/abs/astro-ph/0310784 ] may involve details of the collision between the two galaxies, or alternatively, interactions between a galactic center black hole [ http://antwrp.gsfc.nasa.gov/apod/ap001220.html ] and the surrounding intracluster gas [ http://www.astr.ua.edu/keel/galaxies/icm.html ]. NGC 1275, pictured above [ http://www.noao.edu/image_gallery/html/im0990.html ], spans about 100,000 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] and lies about 230 million light years distant toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Perseus [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Perseus.html ]. |
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The Stars of NGC 300
| Title |
The Stars of NGC 300 |
| Explanation |
Like grains of sand [ http://astronomy.swin.edu.au/staff/gmackie/billions.html ] on a cosmic beach, individual stars of large spiral galaxy NGC 300 [ http://heritage.stsci.edu/2004/13/ ] are resolved in this sharp image from the Hubble Space Telescope's Advanced Camera for Surveys (ACS [ http://hubblesite.org/sci.d.tech/nuts_.and._bolts/ instruments/acs/ ]). The inner region of the galaxy is pictured [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2004/13/fastfacts/ ], spanning about 7,500 light-years. At its center is the bright, densely packed galactic core surrounded by a loose array of dark dust lanes mixed with the stars in the galactic plane. NGC 300 lies 6.5 million light-years away and is part of a group of galaxies [ http://www.seds.org/messier/xtra/ngc/sclgr.html ] named for the southern constellation Sculptor. Hubble's unique ability to distinguish so many stars [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2004/13/ ] in NGC 300 [ http://antwrp.gsfc.nasa.gov/apod/ap020821.html ] can be used to hone techniques for making distance measurements [ http://www.astro.ucla.edu/~wright/ distance.htm ] on extragalactic scales [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/ debate96.html ]. |
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The Colliding Galaxies of NG
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| Title |
The Colliding Galaxies of NGC 520 |
| Explanation |
Is this one galaxy or two? The jumble of stars, gas, and dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] that is NGC 520 is now thought to incorporate the remains of two separate galaxies. A combination of observations and simulations indicate the NGC 520 [ http://www.kopernik.org/images/archive/n520.htm ] is actually the collision of two disk galaxies. Interesting features of NGC 520 include an unfamiliar looking tail of stars [ http://antwrp.gsfc.nasa.gov/apod/ap040515.html ] at the image bottom and a perhaps more familiar looking band of dust [ http://antwrp.gsfc.nasa.gov/apod/ap031008.html ] running diagonally across the image center. A similar looking collision might be expected were our disk Milky Way Galaxy [ http://www.seds.org/messier/more/mw.html ] to collide [ http://www.cita.utoronto.ca/~dubinski/merger/bigmerger.html ] with our large galactic neighbor Andromeda [ http://antwrp.gsfc.nasa.gov/apod/ap040718.html ] (M31). The collision that defines NGC 520 [ http://www.cv.nrao.edu/~jhibbard/n520/n520.html ] started about 300 million years ago and continues today. Although the speeds of stars are fast, the distances are so vast that the interacting pair will surely not change its shape noticeably during our lifetimes. NGC 520 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005MNRAS.359..455R ], at visual magnitude [ http://en.wikipedia.org/wiki/Apparent_magnitude ] 12, has been noted to be one of the brightest interacting galaxies on the sky, after interacting pairs of galaxies known as the Antennae [ http://antwrp.gsfc.nasa.gov/apod/ap971022.html ]. NGC 520 was imaged above [ http://www.gemini.edu/index.php?option=content&task=view&id=150&Itemid=0&limit=1&limitstart=1 ] in spectacular fashion by the Gemini Observatory [ http://antwrp.gsfc.nasa.gov/apod/ap030909.html ] in Hawaii [ http://en.wikipedia.org/wiki/Hawaii ], USA [ http://www.cia.gov/cia/publications/factbook/geos/us.html ]. Also known as Arp [ http://www.haltonarp.com/ ] 157, NGC 520 lies about 100 million light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] distant, spans about 100 thousand light years, and can be seen with a small telescope toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of the Fish (Pisces [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=66 ]). |
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![Copyright: AURA [ http://www.aura-astronomy.org/ ] Explanation: Do star clusters form when galaxies collide? Quite possibly, according to Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap970306.html ] observations of the "Antennae [ http://wwwatnf.atnf.csiro.au/people/bkoribal/antennae.html ]", two galaxies thought to be in the early stages of a collision. As NGC 4038 and NGC 4039 [ http://crux.astr.ua.edu/gifimages/ngc4038.html ] slowly merge, the combined gravity of each pulls the other apart, huge gas clouds collide, and new bright stars and dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap961119.html ] are dispersed. Many blue knots of stars appear to be newly formed globular clusters [ http://antwrp.gsfc.nasa.gov/apod/ap970214.html ]. Red star knots [ http://isowww.estec.esa.nl/activities/info/iso_pr96/ngc4038.html ] are particularly interesting, as they might be globular clusters [ http://www.limber.org/globs.html ] that have not yet expelled early dust from their system. The above picture [ http://archive.stsci.edu/cgi-bin/hst_proposal_search?proposal_id=304&action=search&show=data+abs ] is centered around the smaller of the two interacting galaxies: NGC 4039. The color contrast [ http://oposite.stsci.edu/pubinfo/LookLike/ ] in the above three-color mosaic was chosen to highlight extended features.](http://mm04.nasaimages.org/MediaManager/srvr?mediafile=/Size1/NVA2-4-NA/8258/ngc4039_hst_big.jpg&userid=1&username=admin&resolution=1&servertype=JVA&cid=4&iid=NVA2&vcid=NA&usergroup=NASA_Astronomy_Picture_of_the_Day_Collecti-4-Admin&profileid=16)
![Copyright: AURA [ http://www.aura-astronomy.org/ ] Explanation: This galaxy is having a bad millennium. In fact, the past 100 million years haven't been so good, and probably the next billion or so should be quite tumultuous. NGC 4039 [ http://adsbit.harvard.edu/cgi-bin/nph-article_query?bibcode=1995AJ%2E%2E%2E%2E109%2E%2E960W&page=1&plate_select=NO&type=GIF&nosetcookie=1 ] was a normal spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap970419.html ], minding its own business, when NGC 4038 [ http://antwrp.gsfc.nasa.gov/apod/ap970506.html ] crashed into it. The evolving wreckage, known as the "Antennae [ http://galileo.ifa.hawaii.edu/~hibbard/n4038/n4038.html ]", is pictured above. As gravity [ http://loner.ccsr.uiuc.edu/cyberprof/physics/101/Lecture/L13P3.html ] pulls each galaxy apart, clouds of gas slam into each other and bright blue knots are formed. These knots are large clusters of stars imbedded in vast regions of ionized hydrogen gas [ http://www.phys.unm.edu/~duric/l2h/l6/node1.html ]. The high abundance of relatively dim star clusters is quite unlike our Milky Way's globular cluster system [ http://www.limber.org/globs.html ], though. Perhaps some of these young star cluster [ http://antwrp.gsfc.nasa.gov/apod/ap970214.html ]s will go on to form globular clusters [ http://antwrp.gsfc.nasa.gov/apod/ap961004.html ], while others will disperse through close gravitational encounters. The above picture [ http://archive.stsci.edu/cgi-bin/hst_proposal_search?proposal_id=304&action=search&show=data+abs ] is centered around the larger of the two interacting galaxies: NGC 4038. The diagonal streak across the upper left is unrelated to the colliding galaxies. The color contrast [ http://oposite.stsci.edu/pubinfo/LookLike/ ] in the above three-color mosaic was chosen to highlight extended features.](http://mm04.nasaimages.org/MediaManager/srvr?mediafile=/Size1/NVA2-4-NA/8267/ngc4038_hst.jpg&userid=1&username=admin&resolution=1&servertype=JVA&cid=4&iid=NVA2&vcid=NA&usergroup=NASA_Astronomy_Picture_of_the_Day_Collecti-4-Admin&profileid=16)
